My six-year-old grandson has suddenly developed a toilet phobia. He will not use the toilet for bowel movements anymore. He has been doing it in his pants for the last three days. My daughter had to get him from school today because the teacher called and said that he had an accident. We think his fear started when the toilet overflowed. He begs his mom not to flush it or please wait until he leaves the room. We've tried talking to him and reasoning with him to no avail. Any suggestions will be greatly appreciated.